Anchor bolts (cast-in or post-installed) are commonly used in residential and commercial construction, as well as industry, for the purpose of anchoring columns, sill plates, post bases, hold-downs, machinery and other structural or industrial components to concrete foundations and slabs, or other base materials such as rock or metal fabrications. Anchor bolts typically must be designed with sufficient embedment into the base material to resist applied combinations of shear and uplift forces.
Anchor bolts projecting from concrete typically have a length above the surface that is dependent on the type of element that will be attached to the bolts as well as other engineering, detailing and construction considerations. Because of the projection, it is a frequent occurrence for bolts to be damaged, bent over or broken off during construction activities by heavy equipment that is being used around the bolts prior to the placement of the column or other element to be attached. This damage to the anchor bolt can cause increased construction costs, construction delays, and other adverse consequences. Moreover, a protruding bolt may present a safety hazard on a construction site.
There are a number of methods that have been developed in the field to attempt to protect projected bolts from impacts and damage during construction and to reduce safety hazards, such as drilling holes in wood blocking and securing it with nuts and washers. However, those methods provide little, if any, protection against damage by heavy equipment, and are rarely employed due to the time and effort involved in their implementation. While certain anchor bolt cap products and designs are currently known, the known designs only protect projected bolts from corrosion and degradation that could compromise the fastener's structural integrity or make it difficult to either attach the nuts to the bolt or unscrew them at a later time. Corrosion is rarely an issue with column and sill plate anchor bolts, as they are typically not exposed for a long enough time for sufficient corrosion to affect either fastener integrity or to prevent fastening of the nut. Likewise, for anchor bolts used in building construction, the unfastening of connections at a later time is usually not required or desired.